In co-pending U.S. Patent Application Ser. No. 411,538, filed Oct. 31, 1973, now U.S. Pat. No. 3,910,122, a rotor-less rate sensor that measures angular velocity is described. The means employed therein comprises a moving stream of gas. An ion collector disposed in the stream of ionized gas senses changes by the amount of ions collected. In another co-pending applicaton, U.S. Patent Applicaton Ser. No. 408,313, filed Oct. 23, 1973, now U.S. Pat. No. 3,910,123, there is described a rotor-less angular velocity measuring apparatus wherein a radioactive gas releases ions to an electrode and the number of ions reaching the electode is a measure of the angular velocity of the vehicle upon which the sensor is mounted. These devices teach the measurement of inertial rate without the use of rotors of conventional rate gyros and have application in rate damping, gun sight stabilization and directional control among other applications.
Conventionally, the method of measuring rate was to operate a gyroscope in the captured mode while monitoring the current required to maintain the gyro at null. The measured current in this method is proportional to the applied torque and therefore to gyro rate. The disadvantages of the captured gyro wheel as compared with a rotor-less sensor are numerous. Gyroscopes are difficult and costly to manufacture, primarily because of the high tolerances required in machining and the high degree of skill needed for assembly.
Rotor-less rate sensors as described above, work on the principle of measuring the rate of case experiencing a rotation as it sweeps past an area of ionized gas contained inside the case. The gas catches up to the case with a time constant that is proportional to its density (.rho.) and inversely proportional to its viscosity (.mu.). It is desirable to make this .rho./.mu. as large as possible. It is apparent that a factor of 30:1 can be gained in going to a liquid and holding the other dimension constant. This gain can either be translated into a smaller device with equal performance or a similar size device with improved characteristics.
The method of ionization by radioactive bombardment is not practical for liquids because of the greatly decreased range of the ionizing radiation.
The electrolytic conduction taught by the present invention is unlike conduction in a metal in that electrons do not flow with the speed of light. Instead, when a field is applied across an electrolyte there is a slow drift of ions through the liquid. The current measured is a measure of the number of ions reaching an electrode per unit time. When a flow is imparted to the fluid in such a manner as to oppose the flow of ions, the measured current decreases. On the other hand, when the flow is with the direction of ion movement the current increases.